The present invention relates to heat curable organopolysiloxane fluids well known in the art which utilize a silicon hydride siloxane fluid, silicon vinyl siloxane fluid, an effective amount of a platinum catalyst, an inhibitor which prevents premature gelation and a cure accelerator composed of silicon dihydride and trihydride monomers. More particularly the present invention relates to the use of the silicon dihydrides and trihydrides which accelerate the cure of addition cure silicone formulations. These formulations are useful as release coatings on paper, plastic, and similar substrates. These formulations are also useful as potting compounds, conformal coatings of electronic parts, etc.
Special mention is made of Schilling, Jr., U.S. Pat. No. 4,614,812 and Lewis, L. N. et al., J. Am. Chem. Soc., vol. 108, pp. 7228 (1986) which have reported that the use of small quantities of an SiH compound accelerates the rate of addition cure silicones.
Recently it has been shown that platinum catalyzed hydrosilation of R.sub.2 SiH.sub.2 or RSiH.sub.3 containing silanes is difficult or nearly impossible to carry out. In Lewis et al., Organometallics, vol. 9, pp. 621-25 (1990), it was reported that the SiH.sub.2 or SiH.sub.3 poisoned the platinum catalyst.
Surprisingly, contrary to the suggestions of the prior art, the present applicants have now found that the addition of small amounts of SiH.sub.2 and/or SiH.sub.3 acts to accelerate the rate of cure of platinum catalyzed addition curable silicone materials. This is entirely unexpected in light of the teachings of the prior art that the di and tri hydride silanes are poisons to the platinum catalyst. As shown in the working examples, hereinbelow, the addition of the R.sub.2 SiH.sub.2 and/or RSiH.sub.3 silane additives to a platinum catalyzed addition curable silane system accelerates the cure of the silane so that curing is effected at faster rates and at lower temperatures than silane curing systems of the prior art.